init

2026-10-21 19:32:02 -04:00
commit b74d278c8e
96 changed files with 54476 additions and 0 deletions
@@ -0,0 +1,41 @@
+export const rad = (degrees) => (degrees * Math.PI) / 180;
+export const deg = (radians) => (radians * 180) / Math.PI;
+export const wrap360 = (degrees) => ((degrees % 360) + 360) % 360;
+export const wrap180 = (degrees) => ((degrees + 180) % 360 + 360) % 360 - 180;
+
+/** Convert azimuth clockwise from north and altitude above the horizon to a unit ENU vector. */
+export function azAltToVec(az, alt) {
+  const a = rad(az), e = rad(alt), ce = Math.cos(e);
+  return [ce * Math.sin(a), ce * Math.cos(a), Math.sin(e)];
+}
+
+/** Convert an east/north/up vector to azimuth clockwise from north and altitude. */
+export function vecToAzAlt(vector) {
+  const [east, north, up] = vector;
+  const horizontal = Math.hypot(east, north);
+  return { az: wrap360(deg(Math.atan2(east, north))), alt: deg(Math.atan2(up, horizontal)) };
+}
+
+/** Quaternion [x,y,z,w] conjugate. */
+export function quatConj([x, y, z, w]) {
+  return [-x, -y, -z, w];
+}
+
+/** Rotate a 3D vector by quaternion [x,y,z,w]. */
+export function quatRotate([x, y, z, w], [vx, vy, vz]) {
+  const tx = 2 * (y * vz - z * vy);
+  const ty = 2 * (z * vx - x * vz);
+  const tz = 2 * (x * vy - y * vx);
+  return [
+    vx + w * tx + (y * tz - z * ty),
+    vy + w * ty + (z * tx - x * tz),
+    vz + w * tz + (x * ty - y * tx),
+  ];
+}
+
+/** Great-circle angular separation of two azimuth/altitude positions, in degrees. */
+export function angularSeparation(az1, alt1, az2, alt2) {
+  const a1 = rad(alt1), a2 = rad(alt2), da = rad(wrap180(az2 - az1));
+  const cosSep = Math.sin(a1) * Math.sin(a2) + Math.cos(a1) * Math.cos(a2) * Math.cos(da);
+  return deg(Math.acos(Math.max(-1, Math.min(1, cosSep))));
+}